World-weary journalist Martin Sixsmith (Steve Coogan) and devout Catholic Philomena Lee (Judi Dench) make an odd pairing who inevitably develop mutual respect as together they make efforts to track down Philomena’s son, Anthony, taken for adoption when she was still a teenager.

Wildly different backgrounds are revealed early on when Lee and Sixsmith first meet over a meal at The George, a Harvester restaurant on Bury Street at Sharps Lane, in Ruislip, northwest of London, and the writer reveals he prefers his little local place in Knightsbridge.

Northern Ireland stands in for the Republic of Ireland, as Martin apparently drives into the village of ‘Birr’ to pick up Philomena on the way to ‘Roscrea Convent’, where she last saw her child.

The village is Rostrevor, in Newry and Mourne, County Down, at the foot of Slieve Martin on the coast of Carlingford Lough. Martin crosses the bridge over the Kilbroney River, as Philomena waits on Bridge Street opposite the Killowen Bar, with the beautiful mountains of Mourne on the skyline.

The ‘Sisters of Mercy Convent at Roscrea’, supposedly in ‘County Tipperary’, is back in England.

The convent proper is Harefield House, part of Harefield Grove Farm, a small estate a few miles northwest of Ruislip (and just a few miles from Pinewood Studios). The red-brick laundry building, which seems to adjoin it, is actually about 20 miles away. This is part of Shirburn Castle, Castle Road, Shirburn in Oxfordshire. It’s a measure of the advances in screen technology that, even in a relatively low budget production, these two places are blended together so convincingly.

The overgrown cemetery for mothers and children, which features so importantly later on, is also at Shirburn.

After getting precious little information at the convent, apart from learning that little Anthony was adopted by an American couple, Philomena and Martin retire to the pub, where they learn about the suspiciously convenient fire which destroyed the convent’s records while leaving Roscrea itself miraculously undamaged.

The bar is the Dufferin Arms, 35 High Street, Killyleagh, Downpatrick. This is back in Northern Ireland – as Steve Coogan’s DVD commentary points out, the prominently displayed bottle of Bells whisky would have been unthinkable in the Republic.

Wherever possible, scenes were filmed in the UK so, although the pair arrive at the Washington Court Hotel, 525 New Jersey Avenue Northwest in Washington DC (and Sixsmith is seen jogging on The Mall, past the Smithsonian Building, and on the phone at Tidal Basin), the hotel rooms were filmed in the London Marriott Hotel Regents Park, 128 King Henry's Road, NW3, at Swiss Cottage. The view of the Capitol dome from the window was, need I say, added digitally.

One place that had to be filmed on location is the Lincoln Memorial – as Philomena says: “I’ve always wanted to see him in his big chair.” This brought its own problems. The monument is subject to all kinds of restrictions when it comes to filming – particularly at night. No more than five people are allowed in the chamber at one time (including the film crew), and there’s no sound recording or film lighting permitted. The hot dog stand alongside which Philomena and Martin talk is an ingenious way to get both light and recorded dialogue into the scene.

After having uncovered all they can about Anthony’s life, the pair head back to the airport. Philomena’s recollections of a repressed and guilt-inducing era contrast with the glimpse from the cab window of a joyously unselfconscious couple embracing in the street outside Chinatown Express Restaurant, 746 6th St NW.

At the airport, there’s a change of heart and a return to the city to dig a little deeper. The library in which they start to get a better understanding of Anthony, renamed Michael by his adoptive parents, is the Folger Shakespeare Library, 201 East Capitol Street SE. An independent research library on Capitol Hill, it’s home to the world's largest collection of materials relating to William Shakespeare and to rare Renaissance books and artworks.

Their discoveries prompt them to visit Michael’s one-time partner, Peter Olsson, at his home in Maryland. Increasingly perturbed by the narrative that’s beginning to piece together, Philomena insists on stopping at a roadside church for confession.

The church is St. Paul's Community Church, 14730 Sugarland Lane in Poolesville, in Maryland, about 25 miles northwest of DC. Sugarland Forest Community was established in 1he 1800s by freed slaves, operating as an autonomous Black township with its own church, school and post office. A considerable drop in population since the 1970s means that St Paul’s no longer holds regular weekly services, but it’s claimed to be the site of the first interracial marriage in the USA. It’s not a Roman Catholic church, by the way – the confessional boxes and Stations of the Cross were added for the film.

The final part of the jigsaw falls into place when they finally meet Peter (Peter Hermann) at his home, 10600 River Road in Potomac, one of Maryland's most affluent towns. It’s the John McDonald House, built in 1873 for Captain John McDonald, Irish immigrant and local politician, and the man responsible for changing the name of the community to Potomac.